One question should be "Where does abuse start, where does it stop?" That alone is difficult to define. I have observed - even on myself - that the (moral?) boundary shifts the richer you get. In the beginning I never used a selfvote - I'm not my biggest fan myself. I even found it disgusting when I saw this - even with small users - in others. At some point the penny dropped that the quality of the articles had long since become a minor matter and that's when I lost any "shame" as well.

Maybe 'diminishing returns' are a solution, but also a bit unfair to those who are very diligent, each article is a very good one and for this reason alone I want to support them regularly.
Since the rigorous solution - each user only one account, selfvotes forbidden - is not possible in this system, there is no meaningful control in my opinion. And on the insight of the people can unfortunately not bet.

Flags are okay. But who uses them? Most people are afraid of a flagwar and without a "higher instance", it is anyway hardly possible to find out every selfvoter, every votebuyer.
If I see that a user has bought excessive votes or does so regularly, I won't vote. Others only vote because they know exactly that the user pays bots and so they get a higher CR if they are earlier than the bot.

How you do it, you do it wrong - we cannot change people and their attitudes. But it's certainly always good to call a spade a spade and provoke new thinking, as you do here.
I won't let myself be annoyed by the circumstances any more. As long as I enjoy it, I blog. Those who like my texts, vote for them, those who don't like them, leave them alone. I don't question it anymore - sometimes I still grin... ;-)